This invention relates to a muffler for an engine, particularly a motorcycle engine, for reducing the noises produced by exhaust emissions of the engine.
In one type of muffler for an engine, a sound-absorbing means formed as of glass fibers in mounted in a muffler body connected to an exhaust pipe and secured in place by a keep means in the form of a perforated plate, for example, so as to reduce the noises produced by the muffler body when it vibrates.
The aforesaid type of muffler of the prior art is shown in FIG. 1, wherein a muffler body 1 is composed of two halves 2 and 3 welded together and having sound-absorbing members 4 and 5 attached to the inner surfaces thereof respectively. The sound-absorbing members 4 and 5 are secured to the muffler body 1 by keep members 6 and 7 respectively. When the muffler of the aforesaid construction is fabricated, the sound-absorbing members 4 and 5 are attached to the respective halves 2 and 3 and secured in place by the respective keep members 6 and 7. The keep members 6 and 7 are joined as by spot welding to the halves 2 and 3 at their edges 6a and 7a respectively. Then, the two halves 2 and 3 are joined as by welding at the seams.
In the muffler fabricated as aforesaid, the muffler body produced by welding the two halves together into a unitary structure has on its outer surface dents or marks produced at the time the welding is performed, which spoil the good external appearance of the muffler, particularly when it is used with a motorcycle, if they are left unattended. For this reason, the muffler is subjected to after-treatment, such as buffing, to remove the dents or marks from the muffler body. The step of buffing the muffler body, as well as the steps of securing a plurality of sound-absorbing members to the respective halves of the muffler by means of the respective keep members, makes the muffler fabricating operation time consuming and requiring a lot of labor. The problem with regard to the dents or marks formed when welding is performed may be obviated by producing the muffler body in cylindrical form by form rolling from the beginning. However, difficulties will be encountered in attaching the sound-absorbing members to the cylindrical muffler body, so that it would become impossible to use the sound-absorbing members for reducing the noises produced by the muffler body when it vibrates.